It looks like the electrical gremlins are at work in my 930.
I recently replaced a dead PermaTune CDI with a Bosch unit. At the same time, I checked out all the wiring (including the dreaded green one) and the voltage regulator and couldn't find any problems that might have fried the CDI, but in the two weeks since then, the car has started running very roughly when cold and when I crank the engine, the tacho reads 3-4000 revs

When it is warmed up, it runs fine and is still really strong on boost. Keep in mind that "cold" here is about 20*C, not F.

I am going to launch into this today to try and find the problem, but any hints would be appreciated.
Surely someone out there can join the dots for me:

tacho reads 4000 when cranking (but stable otherwise)

very rough running when cold

plenty of power once boost comes in

AFRs when running rough are 13-14 (I would have expected much lower if ignition is misfiring)

I wrote the equivalent terminal numbers on my wiring diagram at home so I can't confirm right now, but the Bosch and PermaTune CDIs are directly interchangeable with same connector on both, so there shouldn't be any difference.
Thanks for coil specs. I'll check that tonight.

is the bosch unit used or rebuilt or verified it works? could be the ignition part is good but tach output is bad.

you might check control pressures/sys pressure.
air leaks.

is it rough at idle only or when driving
voltage reg. how did you check it. multi meter on battery?
did you check AC ripple at batt
is the alt light on with key on engine off.
did you change coil and CD or just CD?

i think i have seen this problem here, try searching. i know its a pain weeding thru the crap.